KIEV, Ukraine — A column of Russian tanks and armored vehicles entered southeastern Ukraine about dawn Monday, a Ukrainian official said — a move that brings conflict to an area that escaped the intense fighting of recent weeks.

The incursion came one day ahead of a summit that includes both Russian President Vladimir Putin and Ukrainian President Petro Poroshenko and could be aimed at pressuring Ukraine into seeking a negotiated end to the conflict rather than a military victory.

Over the last month, Ukrainian forces have made substantial inroads against pro-Russia separatists in eastern Ukraine, taking control of several towns that had been under rebel control since April.

But the advances have come at a high cost — more than 2,000 civilians and at least 726 Ukrainian servicemen have been killed.

There is no independent figure for the number of rebel dead.

Col. Andriy Lysenko, a spokesman for Ukraine’s National Security Council, said the column of 10 tanks, two armored vehicles, and two trucks crossed the border near the village of Shcherbak and that shells were fired from Russia toward the nearby city of Novoazovsk.

He said they were Russian military vehicles bearing the flags of the separatist Donetsk rebels.

The village is in the Donetsk region, but not under the control of the rebels.

The Ukrainian National Guard later said two of the tanks had been destroyed.

In Moscow, Russian Foreign Minister Sergey Lavrov said Monday he had no information about the column.

The reported incursion and shelling could indicate an attempt to move on Mariupol, a major port on the Azov Sea, an arm of the Black Sea.

Mariupol lies on the main road between Russia and Ukraine’s Black Sea peninsula of Crimea, which Russia annexed in March.

Colonel Lysenko said Mariupol for now has enough defenders “to repel any attack of uninvited guests.”

The tanks and armored personnel carriers apparently are not the first military supplies to enter Ukraine.

Several evenings this month, convoys of military weaponry passed with clockwork regularity through Krasnodon, a rebel-held town in eastern Ukraine near the porous border with Russia.

The convoys were seen three times last week by Associated Press reporters, and one carried about 30 units of weaponry and supplies.

All were coming from the direction of Russia and heading west to where pro-Moscow separatists were fighting Ukrainian troops.

NATO and Ukraine have accused Moscow of covertly shuttling heavy artillery and other weapons to the separatists — allegations that Russia routinely denies.

In Belarus today, Mr. Poroshenko and Mr. Putin are among a group of leaders gathering for a summit.

It was unclear whether they will meet one-on-one to discuss the Ukraine crisis.

Mr. Lavrov, the Russian foreign minister, said that he hoped European Union officials, who also will be at the summit, “will come prepared to use their influence on the Ukrainian side.”

In Kiev, Mr. Poroshenko dissolved parliament on Monday and scheduled early elections for Oct. 26.

Mr. Poroshenko had promised during his spring electoral campaign to resolve the standoff between parliamentary deputies of his coalition and the loyalists of former President Viktor Yanukovych, who was deposed by a pro-Western rebellion in late February.

Mr. Poroshenko said parliament was riven by conflict because many of the deputies were “direct sponsors or accomplices” of the separatists who have seized government and security buildings in the Russian-speaking eastern regions of Donetsk and Luhansk.